package com.company.OfferGuide;

public class 青蛙跳台阶问题 {

    public int numWays(int n) {
        if (n == 0) return 1;
        if ( n < 3) return n;
        int[] dp = new int[n + 1];
        dp[1] = 1;
        dp[2] = 2;
        for (int i = 3; i < dp.length; i++) {
            dp[i] = dp[i -1] + dp[i -2];
            if (dp[i] > 1000000007) {
                dp[i] = dp[i] % 1000000007;
            }
        }

        return dp[n];
    }

}
